Trane ReliaTel Diagnostic Manual page 120

CO Sensor Connections (ReliaTel Units with Demand Controlled Ventilation)
2
compromise the 100 ppm differential, the Lower Limit CO
to enforce the 100 ppm differential and to allow the Upper Limit CO
OA Damper Min Position Setpoints
The OA Damper Min Position setpoints will be determined by the position of two onboard
potentiometers located on the RTEM; Building Design Min Position Setpoint (10-50%) and DCV Min
Position Setpoint (0-40%). A 10% differential will be enforced between the Design Min Position
Setpoint and DCV Min Position Setpoint; the DCV Min Position Setpoint will always be 10% less
than the Design Min Position Setpoint. If the unit is configured for DCV and a Remote Min Position
value is present on the P0 and P1 terminals, the Remote Min Position will become the Design Min
Position Setpoint and the 10% differential will not be enforced. If the Remote Min Position is set to
be lower than the DCV Min Position Setpoint, the Remote Min Position setpoint will be used for the
Design Min Position and the DCV Min Position.
Sequence of Operation
When the unit is in the occupied mode, the outdoor-air (OA) damper opens to the DCV Min Position
Setpoint. If the space CO
will close to the DCV Min Position Setpoint. If the space CO
Upper Level CO
space CO
Setpoint, the OA damper position is modulated proportionally between the DCV Min and the
Design Min Position Setpoints. If there is a call for economizer cooling, the outdoor air damper may
be opened further to satisfy the cooling request. See Figure below.
Figure 69. Damper position
When the unit is in the unoccupied mode, DCV control is deactivated.
Note: When using CO
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level is less than or equal to the Lower Limit CO
2
Setpoint, the OA damper will open to the Design Min Position Setpoint. If the
2
level is greater than the Lower Limit CO
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-based DCV with an RTRM (v8.0 or later) and also an RTEM, set the Design
2
Min Position Setpoint to the minimum outdoor airflow required by the local building code.
The DCV Min Position Setpoint is typically based on either 1) the minimum exhaust airflow
rate from the building or 2) the base ventilation rate required to dilute building- or process-
related contaminants. See HVAC Knowledge Center wave52581 for guidance on
determining the CO setpoints and OA damper position setpoints for a given application.
2
Setpoint will be pushed down in order
2
Setpoint to be set as desired.
2
Setpoint, the OA damper
2
level is greater than or equal to the
2
Setpoint and less than the Upper Limit CO
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RT-SVD03G-EN